Patent GB-454451-A (GB)
Title: Improvements in or relating to systems of control for electrically operated lifts
IPC: B66B1/44
Filed: 1935-05-01
Abstract: 454,451. Control of motors. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and CHUBB, A. A., c/o General Electric Co., Ltd., Stoke, Coventry. May 1, 1935, No. 12960. [Class 38 (iii)] Travelling to predetermined limits; non- regenerative braking.-An electrically driven lift is brought to rest at a required position by energizing the driving motor ST, RO, in a reverse direction, the extent of such reverse energization being proportional to the current supplied to the motor during or after starting but before deceleration, and being determined by the position of a step-by-step switch GA positioned in accordance with the said current. Upon operation of a switch SU, self-maintaining relays U, B operate, the former connecting the motor to its supply, and the latter inserting a suitable amount of resistance SA, SB, SC in the rotor circuit. A relay T is then energized from the rotor circuit and energizes a relay V which inserts resistance RD in series with the coil of the relay T, and closes the circuit of the step-by-step switch GA. This switch varies a resistance RG in series with the coil of a relay E energized from a transformer P in accordance with the motor current. When the relay E operates it interrupts the circuit of the switch GA which is thus positioned in accordance with the motor current. As the motor speeds up the relay T releases and energizes a relay R which short-circuits the rotor resistance. When a floor is approached at which stoppage is required the switch SU is opened, and the operation of an inductor relay Y, in response to the lift passing a plate in the lift shaft, releases the relay B to prepare for the insertion of rotor resistances SA, SB, SC as adjusted by contact banks G3, G4, G5 on the switch GA. The relay B also releases the relay R to open the short-circuit on the rotor resistances. A second plate in the lift shaft then operates a relay S which releases the relay U, and upon subsequent release of the relay S, a relay D is energized over contacts U4 to close a reverse circuit for the motor. Thus, the motor is energized in the reverse direction to an extent determined by the position of the switch GA and proportional to the current supplied to the motor at starting. The relay S is operated again when the lift reaches the desired floor and releases the relays D and M to disconnect the motor and apply a holding brake K, the relay N completing a circuit for returning the switch GA to its initial position. In a modification, the switch GA is positioned rather farther for the same value of motor current and is provided with a second actuating magnet which, at the commencement of deceleration, steps the switch back to remove rotor resistance gradually until the relay M is released when the lift is stopped The switch GA may operate or the resistances G3, G4, G5 through contactors. The system is appli cable to lifts controlled by call-storage and floor selecting relays. In the case of a directcurrent motor drive, the control of the reverse energization is effected by armature resistance.